The subject matter disclosed herein generally relates to blade outer air seals in gas turbine engines and, more particularly, to retention members for blade outer air seals.
In gas turbine engines, the first stage Blade Outer Air Seals (BOAS) and Blade Outer Air Seal Supports (BOAS Supports) are often attached to hooks on the High Pressure Turbine (HPT) case. These hooks can either face aft or forward and depending on the direction of the hooks, the BOAS and BOAS Support will need to be assembled from the aft side or from the forward side of the gas turbine engine, respectively. It is beneficial to have the BOAS and BOAS Supports FWD removable for engine maintainability.
If the BOAS and BOAS supports, often lower life components, are accessible from the front they can be easily accessible by simply separating the HPT module from a Diffuser module of the gas turbine engine. The alternative is coming from the rear and having to disassemble and remove all components aft of the first stage BOAS and BOAS supports to get to the first stage BOAS and BOAS supports.
During maintenance operations, the gas turbine engine is often oriented forward face down and the HPT case is pulled upward, requiring the BOAS and BOAS supports to be retained and secured such that gravity cannot disengage these elements during disassembly and/or maintenance operations. In order to prevent the first stage BOAS and BOAS Supports from falling out after separating a HPT case flange from a Diffuser module case flange there is often a bolted flange. The bolted flange is either separate from the HPT/Diffuser flange or is included with the flanges thus making it a triple flange. The flange is integral to a component that retains the first stage BOAS and BOAS supports and this component remains with the HPT after separation of the HPT-Diffuser flange. This technique is effective, but it requires a flanged component, and often additional bolts, which adds significant weight, cost, and part count to the gas turbine engine.